Wireless communications networks are widely deployed to provide various communications services such as telephony, video, data, messaging, broadcasts, and so on. Such networks, which are usually multiple access networks, support communications for multiple users by sharing the available network resources.
The spectrum allocated to such wireless communications networks can include licensed and/or unlicensed spectrum. Licensed spectrum is generally restricted in its use for wireless communications except for licensed use as regulated by a governmental body or other authority within a given region or country. Unlicensed spectrum is generally free to use, within limits, without the purchase or use of such a license. As the use of wireless communications systems continues to increase, the demand for reallocation of additional spectrum for use in many different use cases, including but not limited to telephones, smart phones, PCs, smart meters, remote sensors, smart alarms, mesh nodes, etc.
In many cases, this spectrum is being (or is expected to be) allocated in such a way that paired carriers, utilized in many existing frequency division duplex (FDD) systems, are either not available, or not available in matched bandwidth configurations. Accordingly, time division duplex (TDD) carriers are expected to be utilized in many future deployments for wireless communications systems.